Anyone using these reels and have any advice on brands or models? Trying to find some with good quality that have reel bodies make of solid material that will not bend at the reel stem under pressure of a decent sized fish.

Okuma makes several models which price per feature are hard to beat.  The old gold standard was the Shimano Baitrunner series.  I have a 6500 and the thing is a tank.  But it is also heavy and rather large.  Cabelas salt striker reels have a baitrunner also in medium to large size.  
 
I've hooked things from the Skyway pier in FL that I couldn't stop with my reels and never "bent" a reel stem.  I'm not even sure that's a thing.  Every spinning reel has a drag system to prevent that sort of thing... If you are goliath fishing and want to lock down your drag, don't use a baitrunner anyway.  But they are no less structurally sound than any other spinner.  
 
I have two of these:  https://www.amazon.com/Okuma-Coronado-Baitfeeder-Spinning-Reel/dp/B0088WQBLE  which looks like they replaced with a newer CDX model.  And a couple of the Avenger series.  No complaints.  

Depends what you are using them for I use a bunch of different ones and not had a stem issues from flatheads and carp?

I have an older composite body Cabela's salt striker bait runner. Fishing for blue cats in the James River. I was trying to horse a fish of the bottom in heavy current, and i could see a big gap in the back of the body of the reel because the stem was bent so much. Should have been using heavier gear. Lost the fish, reel was fine. I do look for sturdy bodies and stems now in my heavier spinning reels.

I have an Okuma Avenger 90 and a Cabela’s Saltstriker, I think 50 or 60. Pretty sure the Saltstriker is rebranded Okuma. They work fine for me. I caught a 50lb+ southern ray on the 90, that peeled probably 100 yards of line before I tightened it down to stop him. I didn’t notice any bend in the stem or anywhere in the reel. The reel is pretty massive, it works fine with a surf rod, but would be out of balance with much smaller. The Saltstriker has caught some 30” slammer bluefish with no issues as well as flatheads. I did let the drag do it’s job on those though.